C Code: How does these even work?

Question

I just saw this here

#include 

int main(int argc, char *argv[printf(\"Hello, world!\\n\")]) {}

What this does is print \"Hello

Answer 1

char *argv[printf("Hello, world!\n")])

printf() returns the number of characters printed.

So

int main(int argc, char *argv[printf("Hello, world!\n")]) {}

is equivalent to

int main(int argc, char *argv[14]) {}

plus a call to printf() which prints "Hello World"